The present invention relates to hydraulic shock absorbers for motor vehicles, and more particularly to a shock absorber having a valved piston that progressively becomes more restrictive to the flow of fluid between the pressure chambers within the shock absorber during the service life of the shock absorber.
In a conventional automative suspension system jounce and rebound movement is damped both by the friction in the system and by a hydraulic shock absorber. During repeated cycling of the suspension system there will be a lessening of the friction in the various pivots of the suspension and, consequently, a reduction in friction damping. In order to compensate for changes in the friction damping characteristics of a vehicle suspension during its service life, it is an object of the present invention to provide a shock absorber which becomes stiffer and increases its damping ability during usage.